1. Field of the Invention
This invention relates to a method of increasing the coercivity of a magnetic device having a magnetite film reduced from alpha ferric oxide.
The coercivity of a magnetic material is one of the properties of the material which determine the strength of the magnetic field necessary to initialy magnetize or thereafter to cause a change in the direction of the magnetization of the material. It is also one of the parameters that determine the information density that can be recorded in and stored by the material. For example, digital information, each discrete amount of information being called a bit, is recorded on an area or region of a recording medium by magnetizing that region in a desired manner. This magnetized region will set up a magnetic field of its own which represents the recorded information. However, if the coercivity of a material is low and adjacent magnetized regions are too close, the magnetic field of one region will affect the magnetization of an adjacent region thereby causing incorrect information to be recorded. Therefore, there must be sufficient distance between two adjacent regions to avoid interaction between the magnetic field of each. The higher the coercivity of the material the less affect such a magnetic field will have on surrounding magnetic material and, therefore, the interaction between the magnetic fields of two adjacent magnetized regions representing two adjacent bits will be less. Consequently, with higher coercivity the recorded bits can be located closer to each other resulting in higher recorded information density. Magnetic films with high coercivity are especially useful in the fabrication of magnetic recording and storage devices used in data processing computers for storing digital information or in any other equipment where analog or digital information storage is desired.
2. Description of the Prior Art
Most presently available magnetic recording and storage devices comprising a magnetite or other all iron oxide film as the storage medium, have a coercivity value of about 200 to 300 Oe. (Oersteds). Some complicated and expensive laboratory methods of fabricating iron oxide maagnetic films have produced devices having a maximum coercivity value of around 400 Oe. Devices having a magnetic film made of cobalt have been produced which have coercivity values as high as 900 Oe. These cobalt films, however, are expensive and somewhat difficult to produce. Inability to economically and readily produce iron oxide film magnetic devices having coercivity values above 300 Oe., has resulted in the use of devices normally having a coercivity value somewhat less than 300 Oe. Consequently, the level of information storage per unit area of such commonly used devices is significantly less than desired.